Hydrogenation techniques are an important means for heavy oil lightening and light oil quality upgrading. Hydrocracking techniques have been developed rapidly because of their advantages such as high adaptability to feedstocks, high product flexibility, high yield of liquid products, and high product quality. Hydrocracking techniques use two types of catalysts, i.e., hydrocracking pretreatment catalysts and hydrocracking catalysts, wherein, hydrocracking catalysts can be categorized into different types of catalysts according to the use of different cracking components. Main cracking components include amorphous silica-alumina, Y zeolites, beta zeolites, SAPO zeolites, and ZSM-5 zeolites, etc. When different types of hydrocracking components are used, the compositions and properties of obtained light oil products are also quite different, and the compositions and properties of the tail oils are also quite different.
The patent document CN103055922B has disclosed a method for preparing a bulk-phase hydrocracking catalyst. The patent documents CN105018139B, CN1293228A, CN1508225A, and CN104611020B have disclosed a hydrocracking method for producing high-quality chemical raw materials at a high yield ratio with low energy consumption, which using two different Y zeolites blended together. Such techniques can use wax oil as feedstock to produce high quality products with a hydrocracking method that uses a hydrocracking catalyst that contain a Y zeolite, wherein, the tail oil has high alkane content and low BMCI value, and is a high-quality raw material for producing ethylene by steam cracking, but each fraction product obtained through hydrocracking is available only in one specification.
The patent document CN105582992A has disclosed a hydro-isomerizing catalyst, a preparation method and an application of the hydro-isomerizing catalyst, and a hydro-isomerizing method for hydrocracked tail oil. Such a technique can use wax oil as feedstock to produce high-quality products with a hydrocracking method that uses a hydrocracking catalyst that contains an isomerizing zeolite, wherein, the tail oil is highly isomerized, has a low solidifying point and a high viscosity index, and is a raw material for high-quality lubricant base oil, but each fraction product obtained through hydrocracking is available only in one specification.
The patent document CN103394368B has disclosed a light oil type hydrocracking catalyst that contains a composite zeolite, and a preparation method and an application of the light oil type hydrocracking catalyst. The patent document CN103551186B has disclosed a middle oil type hydrocracking catalyst that contains a composite zeolite, and a preparation method and an application of the middle oil type hydrocracking catalyst. The patent document U.S. Pat. No. 4,837,396A has disclosed a preparation method of a composite zeolite catalyst. Such techniques can use wax oil as feedstock to produce a variety of high-quality hydrocracked products with a hydrocracking method that uses a composite zeolite hydrocracking catalyst that contains a Y zeolite and an isomerizing zeolite, but each fraction product is available only in one specification.
The patent document CN1169919C has disclosed a method for increasing the yield of high-quality diesel oil with distillate oil. Such a technique can use wax oil as feedstock to produce a variety of high-quality hydrocracked products with a hydrocracking method that uses a hydrocracking catalyst that contains a Y zeolite and a hydrocracking catalyst that contains an isomerizing zeolite at the same time, but each fraction product is available only in one specification.
In summary, it is seen from the comparison of existing hydrocracking techniques that use two different types of zeolite catalysts: among the products obtained with a hydrocracking technique that uses a Y zeolite hydrocracking catalyst, the heavy naphtha product has low sulfur content and relatively high aromatic potential, the jet fuel product has a relatively high smoke point, the diesel oil product has low sulfur content and a high cetane number but a relatively high solidifying point, the tail oil product has low content of aromatic hydrocarbons, relatively low density, a relatively low BMCI value but an extremely high solidifying point usually higher than 30° C.; among the products obtained with a hydrocracking technique that uses an isomerizing zeolite hydrocracking catalyst, the heavy naphtha product has low sulfur content and relatively low aromatic potential content, the diesel oil product has low sulfur content and a low solidifying point but relatively low cetane number, the tail oil has relatively high density but high isomeric hydrocarbon content, and an extremely low solidifying point usually lower than 0° C.; among the products obtained with a hydrocracking technique that uses a Y-isomerizing composite zeolite catalyst or a hydrocracking technique that uses a hydrocracking catalyst that contains a Y zeolite and a hydrocracking catalyst that contains an isomerizing zeolite, the properties of the tail oil are between the properties of the tail oil obtained with a Y zeolite hydrocracking catalyst and the properties of the tail oil obtained with an isomerizing zeolite hydrocracking catalyst. The tail oil products produced with the above-mentioned hydrocracking techniques at the same conversion ratio are quite different from each other, wherein, the tail oil produced with a Y zeolite catalyst is a high-quality raw material for producing ethylene by steam cracking; the tail oil produced with an isomerizing zeolite catalyst can be used directly to produce high-quality lubricant base oil or used as a raw material for high-quality lubricant base oil; the tail oil produced with a Y-isomerizing composite zeolite catalyst or with a Y zeolite hydrocracking catalyst and an isomerizing zeolite hydrocracking catalyst blended together can be used as a raw material for producing ethylene by steam cracking or as a raw material for high-quality lubricant base oil. Therefore, when the above-mentioned hydrocracking processes are used separately, different types of hydrocracking catalysts can be selected as required, or two types of zeolite composite catalysts can be used, or two types of hydrocracking catalysts blended together can be used, but those processes can only produce tail oil products with specific properties depending on the specific process, i.e., the flexibility of operation is relatively poor.